diff --git a/mozilla/string/obsolete/nsString.cpp b/mozilla/string/obsolete/nsString.cpp
index 5ca3b4e563b..38b4aa4fa36 100644
--- a/mozilla/string/obsolete/nsString.cpp
+++ b/mozilla/string/obsolete/nsString.cpp
@@ -383,10 +383,14 @@ nsCString& nsCString::StripWhitespace() {
  */
 nsCString& nsCString::ReplaceChar(PRUnichar aOldChar, PRUnichar aNewChar) {
   PRUint32 theIndex=0;
-  for(theIndex=0;theIndex<mLength;theIndex++){
-    if(mStr[theIndex]==(char)aOldChar) {
-      mStr[theIndex]=(char)aNewChar;
-    }//if
+  
+  if((aOldChar<256) && (aNewChar<256)){
+      //only execute this if oldchar and newchar are within legal ascii range
+    for(theIndex=0;theIndex<mLength;theIndex++){
+      if(mStr[theIndex]==(char)aOldChar) {
+        mStr[theIndex]=(char)aNewChar;
+      }//if
+    }
   }
   return *this;
 }
@@ -399,7 +403,9 @@ nsCString& nsCString::ReplaceChar(PRUnichar aOldChar, PRUnichar aNewChar) {
  *  @return *this 
  */
 nsCString& nsCString::ReplaceChar(const char* aSet, PRUnichar aNewChar){
-  if(aSet){
+  if(aSet && (aNewChar<256)){
+      //only execute this if newchar is valid ascii, and aset isn't null.
+
     PRInt32 theIndex=FindCharInSet(aSet,0);
     while(kNotFound<theIndex) {
       mStr[theIndex]=(char)aNewChar;
@@ -589,7 +595,7 @@ nsCString* nsCString::ToNewString() const {
  * @return  ptr to new ascii string
  */
 char* nsCString::ToNewCString() const {
-  nsCString temp(mStr);
+  nsCString temp(*this);
   temp.SetCapacity(8);
   char* result=temp.mStr;
   temp.mStr=0;
@@ -603,7 +609,7 @@ char* nsCString::ToNewCString() const {
  * @return  ptr to new ascii string
  */
 PRUnichar* nsCString::ToNewUnicode() const {
-  nsString temp(mStr);
+  nsString temp(mStr,mLength);
   temp.SetCapacity(8);
   PRUnichar* result=temp.mUStr;
   temp.mStr=0;
diff --git a/mozilla/xpcom/ds/bufferRoutines.h b/mozilla/xpcom/ds/bufferRoutines.h
index e00ec7259c8..21136d1198b 100644
--- a/mozilla/xpcom/ds/bufferRoutines.h
+++ b/mozilla/xpcom/ds/bufferRoutines.h
@@ -245,7 +245,7 @@ CopyChars gCopyChars[2][2]={
 /**
  *  This methods cans the given buffer for the given char
  *  
- *  @update  gess 3/25/98
+ *  @update  gess 02/17/00
  *  @param   aDest is the buffer to be searched
  *  @param   aDestLength is the size (in char-units, not bytes) of the buffer
  *  @param   anOffset is the start pos to begin searching
@@ -262,8 +262,11 @@ inline PRInt32 FindChar1(const char* aDest,PRUint32 aDestLength,PRInt32 anOffset
   if(aCount<0)
     aCount = (PRInt32)aDestLength;
 
-  if((0<aDestLength) && ((PRUint32)anOffset<aDestLength)) {
- 
+  if((aChar<256) && (0<aDestLength) && ((PRUint32)anOffset<aDestLength)) {
+
+    //We'll only search if the given aChar is within the normal ascii a range,
+    //(Since this string is definitely within the ascii range).
+    
     if(0<aCount) {
 
       const char* left= aDest+anOffset;
@@ -353,7 +356,7 @@ inline PRInt32 FindChar2(const char* aDest,PRUint32 aDestLength,PRInt32 anOffset
 /**
  *  This methods cans the given buffer (in reverse) for the given char
  *  
- *  @update  gess 3/25/98
+ *  @update  gess 02/17/00
  *  @param   aDest is the buffer to be searched
  *  @param   aDestLength is the size (in char-units, not bytes) of the buffer
  *  @param   anOffset is the start pos to begin searching
@@ -371,7 +374,10 @@ inline PRInt32 RFindChar1(const char* aDest,PRUint32 aDestLength,PRInt32 anOffse
   if(aCount<0)
     aCount = aDestLength;
 
-  if((0<aDestLength) && ((PRUint32)anOffset<aDestLength)) {
+  if((aChar<256) && (0<aDestLength) && ((PRUint32)anOffset<aDestLength)) {
+
+    //We'll only search if the given aChar is within the normal ascii a range,
+    //(Since this string is definitely within the ascii range).
  
     if(0<aCount) {
 
diff --git a/mozilla/xpcom/ds/nsString.cpp b/mozilla/xpcom/ds/nsString.cpp
index 5ca3b4e563b..38b4aa4fa36 100644
--- a/mozilla/xpcom/ds/nsString.cpp
+++ b/mozilla/xpcom/ds/nsString.cpp
@@ -383,10 +383,14 @@ nsCString& nsCString::StripWhitespace() {
  */
 nsCString& nsCString::ReplaceChar(PRUnichar aOldChar, PRUnichar aNewChar) {
   PRUint32 theIndex=0;
-  for(theIndex=0;theIndex<mLength;theIndex++){
-    if(mStr[theIndex]==(char)aOldChar) {
-      mStr[theIndex]=(char)aNewChar;
-    }//if
+  
+  if((aOldChar<256) && (aNewChar<256)){
+      //only execute this if oldchar and newchar are within legal ascii range
+    for(theIndex=0;theIndex<mLength;theIndex++){
+      if(mStr[theIndex]==(char)aOldChar) {
+        mStr[theIndex]=(char)aNewChar;
+      }//if
+    }
   }
   return *this;
 }
@@ -399,7 +403,9 @@ nsCString& nsCString::ReplaceChar(PRUnichar aOldChar, PRUnichar aNewChar) {
  *  @return *this 
  */
 nsCString& nsCString::ReplaceChar(const char* aSet, PRUnichar aNewChar){
-  if(aSet){
+  if(aSet && (aNewChar<256)){
+      //only execute this if newchar is valid ascii, and aset isn't null.
+
     PRInt32 theIndex=FindCharInSet(aSet,0);
     while(kNotFound<theIndex) {
       mStr[theIndex]=(char)aNewChar;
@@ -589,7 +595,7 @@ nsCString* nsCString::ToNewString() const {
  * @return  ptr to new ascii string
  */
 char* nsCString::ToNewCString() const {
-  nsCString temp(mStr);
+  nsCString temp(*this);
   temp.SetCapacity(8);
   char* result=temp.mStr;
   temp.mStr=0;
@@ -603,7 +609,7 @@ char* nsCString::ToNewCString() const {
  * @return  ptr to new ascii string
  */
 PRUnichar* nsCString::ToNewUnicode() const {
-  nsString temp(mStr);
+  nsString temp(mStr,mLength);
   temp.SetCapacity(8);
   PRUnichar* result=temp.mUStr;
   temp.mStr=0;
diff --git a/mozilla/xpcom/string/obsolete/nsString.cpp b/mozilla/xpcom/string/obsolete/nsString.cpp
index 5ca3b4e563b..38b4aa4fa36 100644
--- a/mozilla/xpcom/string/obsolete/nsString.cpp
+++ b/mozilla/xpcom/string/obsolete/nsString.cpp
@@ -383,10 +383,14 @@ nsCString& nsCString::StripWhitespace() {
  */
 nsCString& nsCString::ReplaceChar(PRUnichar aOldChar, PRUnichar aNewChar) {
   PRUint32 theIndex=0;
-  for(theIndex=0;theIndex<mLength;theIndex++){
-    if(mStr[theIndex]==(char)aOldChar) {
-      mStr[theIndex]=(char)aNewChar;
-    }//if
+  
+  if((aOldChar<256) && (aNewChar<256)){
+      //only execute this if oldchar and newchar are within legal ascii range
+    for(theIndex=0;theIndex<mLength;theIndex++){
+      if(mStr[theIndex]==(char)aOldChar) {
+        mStr[theIndex]=(char)aNewChar;
+      }//if
+    }
   }
   return *this;
 }
@@ -399,7 +403,9 @@ nsCString& nsCString::ReplaceChar(PRUnichar aOldChar, PRUnichar aNewChar) {
  *  @return *this 
  */
 nsCString& nsCString::ReplaceChar(const char* aSet, PRUnichar aNewChar){
-  if(aSet){
+  if(aSet && (aNewChar<256)){
+      //only execute this if newchar is valid ascii, and aset isn't null.
+
     PRInt32 theIndex=FindCharInSet(aSet,0);
     while(kNotFound<theIndex) {
       mStr[theIndex]=(char)aNewChar;
@@ -589,7 +595,7 @@ nsCString* nsCString::ToNewString() const {
  * @return  ptr to new ascii string
  */
 char* nsCString::ToNewCString() const {
-  nsCString temp(mStr);
+  nsCString temp(*this);
   temp.SetCapacity(8);
   char* result=temp.mStr;
   temp.mStr=0;
@@ -603,7 +609,7 @@ char* nsCString::ToNewCString() const {
  * @return  ptr to new ascii string
  */
 PRUnichar* nsCString::ToNewUnicode() const {
-  nsString temp(mStr);
+  nsString temp(mStr,mLength);
   temp.SetCapacity(8);
   PRUnichar* result=temp.mUStr;
   temp.mStr=0;